ALSA: hda: SPDIF mux controls

Dynamically create mux controls for SPDIF outs on certain IDT/Sigmatel codecs.

Signed-off-by: Matthew Ranostay <mranostay@embeddedalley.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>